Re: [Libguestfs] [PATCH nbdkit 2/3] filters: stats: Measure time per operation

Previously we measured the total time and used it to calculate the rate of different operations. This is incorrect and hides the real throughput. A more useful way is to measure the time we spent in each operation. Here is an example run with this change: $ ./nbdkit --foreground \ --unix /tmp/nbd.sock \ --exportname '' \ --filter stats \ file file=/var/tmp/dst.img \ statsfile=/dev/stderr \ --run 'qemu-img convert -p -n -f raw -O raw -T none /var/tmp/fedora-30.img nbd:unix:/tmp/nbd.sock' (100.00/100%) elapsed time: 2.150 s write: 1271 ops, 1.14 GiB, 0.398 s, 2922.22 MiB/s zero: 1027 ops, 4.86 GiB, 0.012 s, 414723.03 MiB/s extents: 1 ops, 2.00 GiB, 0.000 s, 120470559.51 MiB/s This show that the actual time waiting for storage was only 0.4 seconds, but elapsed time was 2.1 seconds. I think the missing time is in flush() which we do not measure yet.